Role of C nature in correlation structure of soil proprieties in forest and pasture ecosystems, eastern brazilian Amazonia

Author(s): Lydie-Stella Koutika, Carlos Clemente Cerri, Francis Andreux

The improvement of tropical land-use systems is an important task and still further research is necessary to explore the influence of land use and soil properties and environment. Measured soil properties down to 100 cm under a natural forest and pastures cultivated for 7 years under Brachiaria brizantha, 12 years under Panicum maximum, and 17 years under Brachiaria humidicola, were analyzed using principal component analysis in order to extract the correlation structures. Greatest changes following pasture establishment were noticed in the 0-10 cm layer, such as an increase in C stock and in C-derived from pasture associated with the age of pasture. However, there were some changes observed down to 40 cmdepth (a decrease in soil porosity and an increase in clay dispersability). 44.7%of the 26 analyzed variables were explained by the factor 1, and was correlated with C and mainly its nature; 23.9% by the factor 2, which was positively correlated with C content and stock and total porosity; 9.87%by the factor 3, which described the evolution of soil with depth; and by 7.2% by the factor 4, which explained the total variability, describes the interrelation between the storage and the residual porosity.

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